Cortactin-dependent control of Par1b-regulated epithelial cell polarity in Helicobacter infection.

Cell polarity is crucial for gastric mucosal barrier integrity and mainly regulated by polarity-regulating kinase partitioning-defective 1b (Par1b). During infection, the carcinogen Helicobacter pylori hijacks Par1b via the bacterial oncoprotein CagA leading to loss of cell polarity, but the precise molecular mechanism is not fully clear. Here we discovered a novel function of the actin-binding protein cortactin in regulating Par1b, which forms a complex with cortactin and the tight junction protein zona occludens-1 (ZO-1). We found that serine phosphorylation at S405/418 and the SH3 domain of cortactin are important for its interaction with both Par1b and ZO-1. Cortactin knockout cells displayed disturbed Par1b cellular localization and exhibited morphological abnormalities that largely compromised transepithelial electrical resistance, epithelial cell polarity, and apical microvilli. H. pylori infection promoted cortactin/Par1b/ZO-1 abnormal interactions in the tight junctions in a CagA-dependent manner. Infection of human gastric organoid-derived mucosoids supported these observations. We therefore hypothesize that CagA disrupts gastric epithelial cell polarity by hijacking cortactin, and thus Par1b and ZO-1, suggesting a new signaling pathway for the development of gastric cancer by Helicobacter.

Harnessing gastrointestinal organoids for cancer therapy.

Gastrointestinal organoids have emerged as a model system that authentically recapitulates the in vivo situation. Despite biomedical and technical challenges, self-assembled 3D structures derived from pluripotent stem cells or healthy and diseased tissues have proved to be invaluable tools for cancer drug discovery, disease modeling, and studying infection with carcinogenic pathogens.

Fault roughness controls injection-induced seismicity.

Surface roughness ubiquitously prevails in natural faults across various length scales. Despite extensive studies highlighting the important role of fault geometry in the dynamics of tectonic earthquakes, whether and how fault roughness affects fluid-induced seismicity remains elusive. Here, we investigate the effects of fault geometry and stress heterogeneity on fluid-induced fault slip and associated seismicity characteristics using laboratory experiments and numerical modeling. We perform fluid injection experiments on quartz-rich sandstone samples containing either a smooth or a rough fault. We find that geometrical roughness slows down injection-induced fault slip and reduces macroscopic slip velocities and fault slip-weakening rates. Stress heterogeneity and roughness control hypocenter distribution, frequency-magnitude characteristics, and source mechanisms of injection-induced acoustic emissions (AEs) (analogous to natural seismicity). In contrast to smooth faults where injection-induced AEs are uniformly distributed, slip on rough faults produces spatially localized AEs with pronounced non-double-couple source mechanisms. We demonstrate that these clustered AEs occur around highly stressed asperities where induced local slip rates are higher, accompanied by lower Gutenberg-Richter b-values. Our findings suggest that real-time monitoring of induced microseismicity during fluid injection may allow identifying progressive localization of seismic activity and improve forecasting of runaway events.

Inhibition of EIF2α Dephosphorylation Decreases Cell Viability and Synergizes with Standard-of-Care Chemotherapeutics in Head and Neck Squamous Cell Carcinoma.

Drug resistance is a common cause of therapy failure in head and neck squamous cell carcinoma (HNSCC). One approach to tackling it is by targeting fundamental cellular processes, such as translation. The eukaryotic translation initiation factor 2α (EIF2α) is a key player in canonical translation initiation and integrates diverse stress signals; when phosphorylated, it curbs global protein synthesis. This study evaluates EIF2α expression and phosphorylation in HNSCC. A small-molecule inhibitor of EIF2α dephosphorylation, salubrinal, was tested in vitro, followed by viability assays, flow cytometry, and immunoblot analyses. Patient-derived 3D tumor spheres (PD3DS) were cultured with salubrinal and their viability assessed. Lastly, salubrinal was evaluated with standard-of-care chemotherapeutics. Our analysis of RNA and proteomics data shows elevated EIF2α expression in HNSCC. Immunohistochemical staining reveals increasing EIF2α abundance from premalignant lesions to invasive and metastatic carcinoma. In immunoblots from intraoperative samples, EIF2α expression and steady-state phosphorylation are higher in HNSCC than in neighboring normal tissue. Inhibition of EIF2α dephosphorylation decreases HNSCC cell viability and clonogenic survival and impairs the G1/S transition. Salubrinal also decreases the viability of PD3DS and acts synergistically with cisplatin, 5-fluorouracil, bleomycin, and proteasome inhibitors. Our results indicate that pharmacological inhibition of EIF2α dephosphorylation is a potential therapeutic strategy for HNSCC.

Evaluating the prospective crown-root ratio after extrusion and crown lengthening procedures in vitro.

For restoration of extensively damaged teeth preprosthetic treatment measures are necessary. Crown lengthening and extrusion affect the prospective crown-root ratio (CRR). The subject of this in vitro study was to compute CRRs for both treatment approaches. 120 human maxillary central extracted incisors were measured. Measurements were calculated for five treatment groups: C (control), E-2 mm (extrusion of 2 mm), E-4 mm (extrusion of 4 mm), CL-2 mm (crown lengthening of 2 mm), and CL-4 mm (crown lengthening of 4 mm). Tooth (TL), root (RL), and crown lengths (CL) were measured from mesial (m) and facial (f) cemento-enamel junction (CEJ), and respective anatomic (CRR) and effective crown-root ratios (eCRR) were calculated. Following CRR values were computed for C: CRR-m = 0.4 ± 0.1, CRR-f = 0.7 ± 0.1. All crown-root ratios were lower (more favourable) for extrusion compared to crown lengthening (p < 0.001). ECRRs were higher than anatomic CRRs. CRR at mesial CEJ was significantly lower than CRR with facial CEJ as reference (p < 0.001). Mesial measurement-based calculations of CRR typically based on radiographic images should be interpreted with caution as they underestimate the eCRR. CRR can be expected as lower, i.e. more favourable, when teeth are extruded than crown lengthened.

Decreased eukaryotic initiation factors expression upon temozolomide treatment-potential novel implications for eIFs in glioma therapy.

PURPOSE: Since glioma therapy is currently still limited until today, new treatment options for this heterogeneous group of tumours are of great interest. Eukaryotic initiation factors (eIFs) are altered in various cancer entities, including gliomas. The purpose of our study was to evaluate the potential of eIFs as novel targets in glioma treatment. METHODS: We evaluated eIF protein expression and regulation in 22 glioblastoma patient-derived xenografts (GBM PDX) after treatment with established cytostatics and with regards to mutation profile analyses of GBM PDX. RESULTS: We observed decreased expression of several eIFs upon temozolomide (TMZ) treatment independent from the phosphatidylinositol 3-kinase (PI3K)/ AKT/ mammalian target of the rapamycin (mTOR) signalling pathway. These effects of TMZ treatment were not present in TMZ-resistant PDX. Combination therapy of regorafenib and TMZ re- established the eIF/AKT/mTOR axis. CONCLUSION: Our study provides novel insights into chemotherapeutic effects on eIF regulation in gliomas and suggests that eIFs are interesting candidates for future research to improve glioma therapy.

Forced Orthodontic Extrusion to Restore the Unrestorable: A Proof of Concept.

The purpose of this clinical study was to assess the feasibility of forced orthodontic extrusion with the Tissue Master Concept to retain subgingivally fractured teeth as abutments for which extraction and replacement would be equal treatment opportunities. Participants were recruited from a group of consecutive patients in need of prosthodontic rehabilitation. In total, 36 deeply destroyed teeth in 31 patients underwent forced orthodontic extrusion with forces exceeding 50 g to reestablish biologic width and ensure a 2-mm dentin-ferrule design prior to single-crown restoration. The primary endpoint was the success of the extrusion in terms of the ability to restore the respective abutment tooth. Information about overall treatment time, frequency, and reasons for failure were collected. Four patients dropped out of the treatment. For the remaining 27 participants, data were fully collected. The amount of extrusion ranged between 2 and 6 mm (3.5 ± 0.9 mm), and the mean duration until retention was 20 ± 12 days. On average, patients returned three (± 3) times for control visits after extrusion. Adhesive failure (n = 6) and orthodontic relapse (n = 2) were the most frequent complication types. Forced orthodontic extrusion may be a useful tool to restore teeth evaluated as nonrestorable.

Implant or tooth? - A cost-time analysis of managing "unrestorable" teeth✰.

OBJECTIVES: Retaining and restoring severely compromised teeth with subcrestal defect extensions or removing and replacing them using implant-supported crowns (ISC) remains controversial, and economic analyses comparing both strategies remain scarce. We performed a cost-time analysis, comparing the expenditures for retaining "unrestorable" teeth using forced orthodontic extrusion and restoration (FOE) versus extraction and ISC, in a clinical prospective cohort study. METHODS: Forty-two patients (n = 21 per group) were enrolled from clinical routine at a university into this study. Direct medical and indirect costs (opportunity costs) were assessed for all relevant steps (initial care, active care, restorative care, supportive care) using the private payer's perspective in German healthcare based on a micro-costing approach and/or national fee items. Statistical comparison was performed with Mann-Whitney-U test. RESULTS: Patients were followed up for at least one year after initial treatment (n = 40). The drop-out rate was 5% (n = 2). Total direct medical costs were higher for ISC (median: 3439.05€) than FOE (median: 1601.46€) with p<0.001. We observed a higher number of appointments (p = 0.002) for ISC (median: 14.5) in comparison to FOE (median: 12), while cumulatively, FOE patients spent more time in treatment (median: 402.5 min) in comparison to ISC (median: 250 min) with p<0.001, resulting in comparable opportunity costs for both treatment groups (FOE: 304.50€; ISC: 328.98€). CONCLUSIONS: ISC generated higher costs than FOE. More in-depth and long-term exploration of cost-effectiveness is warranted. CLINICAL SIGNIFICANCE: ISCs were associated with higher initial medical costs and required more appointments than the restoration of severely compromised teeth after FOE. Treatment time was higher for patients with FOE, resulting in similar opportunity costs for both treatment approaches. Future research needs to investigate long-term cost-effectiveness.

Root-analogue implants compared to forced orthodontic extrusion: a retrospective analysis of clinical, radiological and esthetic outcomes after restoration.

OBJECTIVES: To assess clinical, radiological and esthetic outcomes of restorations supported by root-analogue implants (RAIs) or roots of severely damaged teeth after forced orthodontic extrusion (FOE). MATERIALS AND METHODS: Clinical data regarding milled one-piece (titanium/zirconia roots and zirconia abutments) RAIs (REPLICATE™ System) and FOE were recorded and retrospectively evaluated for 40 patients by two investigators. Strict inclusion and exclusion criteria were applied. Functional and esthetic outcomes were assessed for n = 20 pre-molars and n = 20 anterior teeth via comparison of radiographic and digital images applying the novel Functional Implant Prosthodontic Score (FIPS). Krippendorff's alpha coefficient was calculated to assess inter-rater reliability. Mann-Whitney-U-Test was used to compare the assessed parameters. Level of significance was set to p < 0.05. RESULTS: After a mean observation period of 18.4 ± 5.7 months for restorations supported by RAIs and 43.9 ± 16.4 months for restorations after FOE, mean FIPS scores were 9.2/8.8 ± 1.1/1.2 (RAIs) and 7.4/7.7 ± 1.3/1.5 (FOE), respectively. Krippendorff's alpha coefficients did not reveal unacceptable inter-rater reliabilities regarding the investigators and applicability of FIPS. Significant differences were documented when comparing restorations after FOE or supported by RAIs regarding bone loss (p < 0.01), presence of papillae (p < 0.05) and quality and quantity of mucosa (p < 0.02) in favor of FOE. CONCLUSIONS: Within the main limitations of sample size and the retrospective study design, both concepts seem to provide clinically acceptable results. CLINICAL RELEVANCE: Bone- and tissue-preserving characteristics regarding the concept of FOE are promising. It could be applicable for socket preservation and subsequent conventional implant placements in an adapted workflow.

Health economic evaluation of forced orthodontic extrusion of extensively damaged teeth: up to 6-year results from a clinical study.

OBJECTIVES: Clinical data on retaining extensively damaged teeth using forced orthodontic extrusion followed by restorative rehabilitation are scarce, and economic evaluations are basically absent. A health economic evaluation of this method was performed based on a clinical study. MATERIALS AND METHODS: In a convenience sample of individuals recruited from routine care, extensively damaged teeth were orthodontically extruded prior to restoration. Patients were followed up for up to 6 years. The health outcome was tooth retention time. Direct medical, non-medical, and indirect initial and follow-up costs were estimated using the private payer's perspective in German healthcare. Association of initial direct medical treatment costs and cofounding variables was analyzed using generalized linear models. Success and survival were secondary outcomes. RESULTS: A total of 35 teeth in 30 patients were followed over a mean ± SD of 49 ± 19 months. Five patients (14%) dropped out during that period. Median initial costs were 1941€ (range: 1284-4392€), median costs for follow-up appointments were 215€ (range: 0-5812€), and median total costs were 2284€ (range: 1453 to 7109€). Endodontic re-treatment and placement of a post had a significant impact on total costs. Three teeth had to be extracted and in three patients orthodontic relapse was observed. The survival and success rates were 91% and 83%, respectively. CONCLUSIONS: Within the limitations of this clinical study, total treatment costs for orthodontic extrusion and subsequent restoration of extensively damaged teeth were considerable. Costs were by large generated initially; endodontic and post-endodontic therapies were main drivers. Costs for retreatments due to complications were limited, as only few complications arose. CLINICAL RELEVANCE: The restoration of extensively damaged teeth after forced orthodontic extrusion comes with considerable initial treatment costs, but low follow-up costs. Overall and over the observational period and within German healthcare, costs are below those for tooth replacement using implant-supported crowns. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: DRK S00026697).

Synthesis and structure-activity relationships of USP48 deubiquitinylase inhibitors.

Ubiquitin-specific proteases represent a family of enzymes that catalyze the cleavage of ubiquitin from specific substrate proteins to regulate their activity. USP48 is a rarely studied USP, which has recently been linked to inflammatory signaling via regulation of the transcription factor nuclear factor kappa B. Nonetheless, a crystal structure of USP48 has not yet been resolved and potent inhibitors are not known. We screened a set of 14 commercially available USP inhibitors for their activity against USP48 and identified the USP2 inhibitor "ML364" as a candidate for further optimization. Using a ligand-based approach, we derived and synthesized a series of ML364 analogs. The IC50 concentrations of the new compounds to inhibit USP48 were determined in a deubiquitinylase activity assay by measuring the fluorescence intensity using tetra-ubiquitin rhodamine110 as substrate. A compound containing a carboxylic acid functionalization (17e) inhibited USP48 activity toward tetra-ubiquitin rhodamine110 with an IC50 of 12.6 µM. Further structure-based refinements are required to improve the inhibition activity and specificity.

The conundrum of Helicobacter pylori-associated apoptosis in gastric cancer.

Helicobacter pylori is a human microbial pathogen that colonizes the gastric epithelium and causes type B gastritis with varying degrees of active inflammatory infiltrates. The underlying chronic inflammation induced by H. pylori and other environmental factors may promote the development of neoplasms and adenocarcinoma of the stomach. Dysregulation of various cellular processes in the gastric epithelium and in different cells of the microenvironment is a hallmark of H. pylori infection. We address the conundrum of H. pylori-associated apoptosis and review distinct mechanisms induced in host cells that either promote or suppress apoptosis in gastric epithelial cells, often simultaneously. We highlight key processes in the microenvironment that contribute to apoptosis and gastric carcinogenesis.

Latent CSN-CRL complexes are crucial for curcumin-induced apoptosis and recruited during adipogenesis to lipid droplets via small GTPase RAB18.

The COP9 signalosome (CSN) and cullin-RING ubiquitin ligases (CRLs) form latent CSN-CRL complexes detectable in cells. We demonstrate that the CSN variants CSNCSN7A and CSNCSN7B preferentially bind to CRL3 or CRL4A and CRL4B, respectively. Interestingly, the interacting protein ubiquitin-specific protease 15 exclusively binds to latent CSNCSN7A-CRL3, while p27KIP attaches to latent CSNCSN7B-CRL4A complex. Inhibition of deneddylation by CSN5i-3 or neddylation by MLN4924 do not impede the formation of latent complexes. Latent CSNCSN7A-CRL3 and latent CSNCSN7B-CRL4A/B particles are essential for specific cellular functions. We found that curcumin-induced cell death requires latent CSNCSN7B-CRL4A. Knockout of CSN7B in HeLa cells leads to resistance against curcumin. Remarkably, the small GTPase RAB18 recruits latent CSNCSN7A-CRL3 complex to lipid droplets (LDs), where CRL3 is activated by neddylation, an essential event for LD formation during adipogenesis. Knockdown of CSN7A or RAB18 or destabilization of latent complexes by cutting off CSN7A C-terminal 201-275 amino acids blocks adipogenesis.

Structural Dynamics of Lys11-Selective Deubiquitinylase Cezanne-1 during the Catalytic Cycle.

Deubiquitinylating enzymes (DUBs) regulate the deubiquitinylation process of post-translationally modified proteins and thus control protein signaling in various cellular processes. The DUB Cezanne-1 catalyzes the cleavage of the iso-peptide bond of Lys11-linked polyubiquitin chains with high selectivity. Crystal structures of Cezanne-1 in different states provide important insight regarding the complex formation and global changes during the catalytic cycle but are lacking details of dynamics and control of activation. Activity-based probes are used to isolate intermediate states upon forming covalent bonds with the DUB active site. Those, however, may lead to structures that are non-native. Conformational changes of Cezanne-1, during its process of activation and proteolytic activity, are investigated using all-atom molecular dynamics (MD) simulations of the ubiquitin-free, diubiquitin-bound, and monoubiquitin-bound Cezanne-1 DUB for a total of ∼18 µs. Our results show that ubiquitin-free Cezanne-1 dynamically shuttles between catalytically competent and incompetent states which suggests that its activation is independent of substrate binding. The catalytically competent substrate-free Cezanne-1 promotes distal ubiquitin substrate access to the catalytic center. The subsequent binding of the proximal ubiquitin shifts the equilibrium toward the catalytically competent state of the dyad, thereby promoting proteolysis of the iso-peptide bond. After cleavage of the scissile bond, sequential dissociation of first the proximal ubiquitin induces the inactivation of Cezanne-1. The subsequent release of the distal ubiquitin fully reconstitutes the inactive substrate-free state of Cezanne-1. The process of activation and catalytic turnover of DUB Cezanne-1 is a multistage cycle with several critical dynamic transitions that cannot be characterized based on protein structures alone. Activity-based probes of cysteine proteases lead to non-native protein-protein contacts, which need to be resolved in order to be able to issue statements about physiological states and substrate binding.

Helicobacter pylori regulates TIFA turnover in gastric epithelial cells.

The human pathogen Helicobacter pylori induces a strong inflammatory response in gastric mucosa manifested by the recruitment of neutrophils and macrophages to the places of infection, and by changes in epithelial integrity and function. At the molecular level, this innate immune response is essentially dependent on the activation of NF-κB transcription factors regulating the expression of chemotactic factors, e.g., IL-8. Recently, it has been demonstrated that the NF-κB signaling pathway is triggered by the bacterial heptose metabolites, which activate the host ALPK1-TIFA axis. TIFA has been suggested to promote oligomerization and activity of the E3 ubiquitin ligase TRAF6, which further stimulates TAK1-IKK signaling. Here, we demonstrate that ALPK1-dependent TIFA activation in H. pylori-infected gastric epithelial cells is followed in time by a decline in TIFA levels, and that this process is impeded by inhibitors of the proteasomal and lysosomal degradation. According to our data, TRAF2, TRAF6, TAK1 or NEMO are not required for TIFA degradation. Additionally, H. pylori promotes the interaction of TIFA with free polyubiquitin as well as with optineurin, TAX1BP1 and LAMP1, which are known protein adaptors involved in intracellular trafficking to lysosomes.

MAPT genotype-dependent mitochondrial aberration and ROS production trigger dysfunction and death in cortical neurons of patients with hereditary FTLD.

Tauopathies are a major type of proteinopathies underlying neurodegenerative diseases. Mutations in the tau-encoding MAPT-gene lead to hereditary cases of frontotemporal lobar degeneration (FTLD)-tau, which span a wide phenotypic and pathological spectrum. Some of these mutations, such as the N279K mutation, result in a shift of the physiological 3R/4R ratio towards the more aggregation prone 4R isoform. Other mutations such as V337M cause a decrease in the in vitro affinity of tau to microtubules and a reduced ability to promote microtubule assembly. Whether both mutations address similar downstream signalling cascades remains unclear but is important for potential rescue strategies. Here, we developed a novel and optimised forward programming protocol for the rapid and highly efficient production of pure cultures of glutamatergic cortical neurons from hiPSCs. We apply this protocol to delineate mechanisms of neurodegeneration in an FTLD-tau hiPSC-model consisting of MAPTN279K- or MAPTV337M-mutants and wild-type or isogenic controls. The resulting cortical neurons express MAPT-genotype-dependent dominant proteome clusters regulating apoptosis, ROS homeostasis and mitochondrial function. Related pathways are significantly upregulated in MAPTN279K neurons but not in MAPTV337M neurons or controls. Live cell imaging demonstrates that both MAPT mutations affect excitability of membranes as reflected in spontaneous and stimulus evoked calcium signals when compared to controls, albeit more pronounced in MAPTN279K neurons. These spontaneous calcium oscillations in MAPTN279K neurons triggered mitochondrial hyperpolarisation and fission leading to mitochondrial ROS production, but also ROS production through NOX2 acting together to induce cell death. Importantly, we found that these mechanisms are MAPT mutation-specific and were observed in MAPTN279K neurons, but not in MAPTV337M neurons, supporting a pathological role of the 4R tau isoform in redox disbalance and highlighting MAPT-mutation specific clinicopathological-genetic correlations, which may inform rescue strategies in different MAPT mutations.

Monolithic hybrid abutment crowns (screw-retained) versus monolithic hybrid abutments with adhesively cemented monolithic crowns.

OBJECTIVES: The objective of this study is to compare monolithic hybrid abutment crowns (screw-retained) versus monolithic hybrid abutments with adhesively cemented monolithic single-tooth crowns. MATERIALS AND METHODS: Twenty subjects in need of an implant-borne restoration were randomly assigned to receive either a cement-retained (CRR) or a screw-retained (SRR) implant-supported monolithic lithium disilicate (LS2 ) reconstruction. Each patient received a titanium implant with in internal conic connection. After osseointegration and second-stage surgery, healing abutments were placed for about 10 days. The type of restoration (CRR vs. SRR) was randomly assigned, and the restorations were manufactured of monolithic LS2 . Both types of restorations, CRR and SRR, were based on a titanium component (Ti-base) that was bonded to the abutment (CRR) or the crown (SRR). The follow-up period for all restoration was 36 months. Clinical outcome was evaluated according to Functional Implant Prosthetic Score (FIPS). Quality of live (OHIP) and patient's satisfaction were assessed using patient-reported outcome measures (PROMs). Primary endpoint was loss of restoration for any reason. Kaplan-Meier curves were constructed and log-rank testing was performed (p < .05). RESULTS: One restoration of group CRR failed after 6 months due to loss of adhesion between Ti-base and individual abutment. No further biological or technical failures occurred. Kaplan-Meier analysis showed no significant difference between both treatment options (p = .317). There was no statistically significant difference between both types of restoration, neither for FIPS, OHIP, treatment time nor patient satisfaction (p > .05). CONCLUSION: Monolithic hybrid abutment crowns (screw-retained) and monolithic hybrid abutment with adhesively cemented monolithic crowns using lithium disilicate showed no statistically significant difference for implant-based reconstructions in this pilot RCT setting.

Forced orthodontic extrusion to restore extensively damaged anterior and premolar teeth as abutments for single-crown restorations: Up to 5-year results from a pilot clinical study.

STATEMENT OF PROBLEM: Clinical data on orthodontic extrusion to restore teeth deemed unrestorable because of their defect size are scarce. It remains unclear for which defects forced orthodontic extrusion and tooth retention is preferred to extraction. PURPOSE: The purpose of this pilot clinical study was to investigate the survival, frequency, and type of complications of extensively damaged teeth requiring single-crown restorations after forced orthodontic extrusion. MATERIAL AND METHODS: Participants were recruited from consecutive patients in need of restorative treatment of extensively damaged teeth at a university clinic. The teeth were orthodontically extruded to reestablish the biologic width and to ensure a 2-mm ferrule preparation before restoration. The primary endpoint was restoration success and survival. At recall, survival was defined as the tooth being in situ and success as a symptom-free tooth with an intact, caries-free restoration and with physiological pocket probing depths, no signs of intrusion, ankylosis, root resorption, or periapical radiolucency. Recalls were performed every 6 months; the outcome was assessed by radiographic and clinical evaluation after up to 5 years of clinical service. Quantitative parameters were described with mean values and standard deviations. RESULTS: Thirty-four participants were assessed for eligibility and enrolled (mean ±standard deviation age: 53.4 ±18.9 years). Four participants were premature dropouts. Data were analyzed for 35 teeth in 30 participants. The amount of extrusion varied between 2 and 6 mm (mean ±standard deviation 3.4 ±0.9 mm). The mean duration of extrusion was 18.9 ±12.6 days and the mean duration of retention was 126.94 ±88.1 days. The mean ±standard deviation crown-to-root ratio after treatment was 0.8 ±0.1 (range: 0.5 to 1.0). Three participants exhibited orthodontic relapse before restoration. Teeth were successfully restored after repeated extrusion. After a mean observation period of 3.3 years (range: 1 to 5.2 years), 29 of 31 teeth were still in situ. Two teeth were fractured, and 4 participants were not available for recall. Thus, the survival rate was 94%. No resorption or periapical translucencies were observed radiographically. Clinical examinations revealed physiological probing depths and absence of ankyloses. One tooth presented with marginal bone loss. The most frequent type of complication was orthodontic relapse at recall (n=3). A total of 84% of teeth were considered a success. CONCLUSIONS: Forced orthodontic extrusion allowed for the restoration of anterior and premolar teeth deemed as nonrestorable because of their defect size. Tooth retention of extensively damaged teeth and their use as abutments for single-crown restorations can be recommended.